[Danh]

Bio balls are made and designed more for their trickle affect than for pure surface area, as submerged bio media is made. They are much more efficient when used as dry media. So lower the water leven in the sump as far as you can. Put some prefilter media on top of the bio balls and you can full up any unused space in your sump with any kind of submerged media... ceramic rings, lava rock, gravel - just watch out that you don't get any in your pump. I wouldn't say that wet/dry sumps are used more often in sw than fw in general, but definitely with smaller tanks <55g or so. I have three FW tanks with wet/drys.. and 90g, 180g and 450g. They all run soely on sumps with 10g, 26g and 50g of bio balls resepectively. The 90 and 180 have have only the bottom inch or so of the bio balls submerged.